The present invention relates generally to tubing/fitting connections and, in an embodiment described herein, more particularly provides a connection for flexible tubing and fittings made of specific materials.
Tubing/fitting connections are well known in the art, and a variety of such connections have been developed over the years. One common connection for a rigid tubing and fitting is to use a ferrule which slips over the tubing and is secured to the fitting by a nut threaded to the fitting. The ferrule externally grips the tubing, and is sealed between the tubing and fitting, when the nut is tightened onto the fitting.
Another common connection for flexible tubing is to form a tubular barb on the fitting, which may be made of either metal or plastic material. The barb is inserted into the tubing and internally grips the tubing. For elevated pressure applications, a clamp is usually installed about the exterior of the tubing. When the clamp is tightened, the tubing is forced against the exterior of the barb, thereby enhancing the sealing of the tubing to the barb and further securing the tubing to the barb.
Unfortunately, each of these connections has drawbacks and, in particular, is unsuitable for use with crosslinked polyethylene (PEX) tubing and/or fittings. The ferrule and threaded nut connection uses an external clamping force to seal the ferrule to the tubing, but does not internally support the tubing. Where flexible tubing is used, this clamping force will collapse the tubing, unless the tubing is internally supported.
The ferrule and threaded nut connection is very unsuitable for use where both the tubing and fitting are made of PEX. Since PEX has a relatively low modulus, threads formed on a fitting would easily deform, and would also make it difficult to produce a consistent force on the ferrule. In addition, it would be difficult to achieve and maintain a seal between the ferrule and the fitting, and between the ferrule and the tubing. Furthermore, since PEX has a relatively low coefficient of friction, it would be difficult for the ferrule to grip the tubing.
The tubular barb connection also has disadvantages. If the tubing and fitting are made of PEX material, the very low coefficient of friction between the tubing and barb will make it very difficult to secure these parts together at elevated pressures. If the barb is made of any flexible material, such as PEX, it will need to have a relatively thick cross-section to resist the clamping force. This thick cross-section will reduce the flow area through the fitting.
From the foregoing, it can be seen that it would be quite desirable to provide an improved tubing/fitting connection and an improved method of connecting tubings to fittings. These improvements should permit satisfactory use with PEX tubings and fittings, and should be usable with other materials as well.
In carrying out the principles of the present invention, in accordance with an embodiment thereof, a tubing/fitting connection is provided in which a retainer is used to secure the tubing to the fitting. The retainer may also internally support the tubing. A clamp may be used to enhance the gripping and sealing engagement between the tubing and fitting. In some embodiments, the retainer may also seal the tubing to the fitting.
In broad terms, a tubing/fitting connection is provided which includes a flexible tubing, a non-rigid fitting having a portion thereon for receiving the tubing, and a retainer which grips the tubing and grips the fitting portion, thereby securing the tubing to the fitting portion. Several embodiments of the retainer are provided. The retainer may internally grip both the tubing and the fitting. The retainer may optionally sealingly engage both the tubing and the fitting. The retainer may be a single member, or it may include multiple members.
A method of connecting a flexible tubing to a fitting is also provided, which method includes the steps of inserting a retainer into the crosslinked polyethylene tubing, internally gripping the tubing with at least one first gripping structure of the retainer, internally supporting the tubing with a cylindrical portion of the retainer, inserting the tubing into the fitting, and internally gripping the fitting with at least one second gripping structure of the retainer.
The use of the disclosed connection and method provides reliable, economical, secure and convenient sealing attachment of tubings to fittings, and is especially useful where the tubing and fitting are made of PEX material.
These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of representative embodiments of the invention hereinbelow and the accompanying drawings.